Padina tetrastromatica

Pagana, Ilaria, Marroccia, Genny, Marletta, Giuliana & Alongi, Giuseppina, 2023, Re-examination of the distribution and species diversity of the genus Padina (Dictyotales, Phaeophyceae) in the Mediterranean Sea, Phytotaxa 619 (3), pp. 205-218 : 213-214

Padina tetrastromatica ( Fig. 6 A–E )

Basionym:— Padina tetrastromatica

Type locality:— Meith (Maydh), Somalia

Distribution in the Mediterranean Sea:— SYRIA ( Mayhoub 2004)

Examined Specimens:— ITALY. Palermo : Punta Raisi, – 2m, 4/5/1966, CAT 1730 as P. pavonica .

Morphology:—The thallus is flabelliform ( Fig. 6A ) and attached to the substrate through a fibrous disc-shaped holdfast. The stipe is short, flattened, and the thallus has a light calcification on the upper surface. The species shows concentric and narrow-undepressed hair lines at an equal distance between both surfaces. The margins are smooth or slightly undulated and the upper rolled portions show a smooth surface. The thallus consists mainly of 4 layers of cells ( Fig. 6D, E ), except in the rolled apical portion where only 2-cell layers are present ( Fig. 6C ); between the 2-cell and 4-cell portions, a short zone with 3 layers of cells can be identified.

In our sample, bands of sori are present near the growth zone and are located on both sides of the hair lines, particularly they are in continuous lines above hair lines and in discontinuous lines below the hair lines ( Fig. 6B ). Moreover, there is no indusium and Vauganiella stage, the latter found instead by Aisha & Shameel (2010).

Remarks:—This Indo-Pacific species was reported in Syria in 2004 ( Mayhoub 2004) but, according to Verlaque et al. (2015:51), its successful establishment in the Mediterranean Sea remains unknown. Our herbarium specimen attests to the presence of P. tetrastromatica in this basin as early as 1966. Therefore, it is very likely that this species could have a wider distribution in the Mediterranean Sea. For this reason, it is very important to accurately examine past data through the study of herbarium sheets to assess the real distribution of this species in the Mediterranean as well as a more accurate identification of new specimens of the genus Padina collected.

Wynne (1998) considered P. tetrastromatica to be a synonym of Padina antillarum (Kützing) Piccone (1886: 36) ; but we, according to Ni-Ni-Win et al. (2011b), retain to maintain the two taxa separate until specimens from the respective type localities have been compared using sequence data.

Figures

FIGURE 6. Padina tetrastromatica. A. Herbarium sheet (CAT 1730) showing habitus. B. Lower surface with continuous lines of sporangial sori above hair lines and discontinuous lines below the hair lines. C. Longitudinal section of the rolled part of the apical portion of the thallus. D. Cross section of the median portion of the thallus showing 4 layers of cells. E. Cross section of the basal portion of the thallus showing 4 layers of cells. All photos refer to the herbarium sheet sample. Scale bars: A, 1 cm; B, 110 μm C–E, 50 μm. Photos by G. Marletta.